Such a ground-working machine and such a method follow from EP 2 395 153 B1 or DE 102 38 646 B3. With these known methods, vertical wall panels can be created very effectively in the ground, wherein they can form a vertical sealing or supporting wall by overlapping.
In order for the thus created walls to achieve an adequate sealing function, the individual wall panels must be created with a very exact position relative to each other. To produce relatively deep, vertical walls, drilling and mixing tools are to be used that have a corresponding length. With increasing length of the drilling and mixing tools, the risk of the drilling and mixing tools going off course as they are lowered into the ground also increases. This can impair not only the sealing function of the whole wall. Rather more, the individual rod-like drilling and mixing tools going off course can result in considerable shear and flexural forces being exerted on the typically 10 to 20 m long drilling and mixing tools. The dynamic stress during driving in rotation of the tools leads, if the tools go off course, to considerable wear and tear on the screw conveyors, the rod-form base body as well as the rotary bearings of the individual tools.
By arranging a transverse yoke and an intermediate guide, as taught in EP 2 395 153 B1, the stiffness of the whole tool can be increased and the extent of an off-course movement thus reduced. When shear forces arise during drilling, for example due to rocks or boulders in the drilling channel, the whole assembly can also be deflected. In this case the wear and tear on the screw conveyors, the rod-form base bodies and the bearings are distributed across the entire drilling and mixing tools.